The invention relates to a decompression device for internal combustion engines to suspend and automatically turn on again compression after several rotations of the engine during the engine start by way of lifting a valve of the engine for a certain time, said decompression device comprising a camshaft operated balancer acting on said valve, a decompression cam rotatable on its own axis and acting on the balancer, and a rotating device to rotate the decompression cam, said rotation device consisting of a ratchet rotatably secured to the balancer and a ratchet wheel with a notchless segment in engagement with the ratchet and rigidly connected with the decompression cam, the axis of the decompression cam being arranged parallel to the axis of the balancer.